Frontend: Adds screenshot of compare cards

[benhammondmusic]

Description and Motivation

• closes #3704
• use report title + card name for downloaded image file name
• rename <HetDialog> to <HetSnackbar>
• makes thumbnail a little bigger on copy img to clipboard preview
• adjusts button label in compare mode to indicate "side-by-side images"
• refactoring of useCardImage hook to allow img copying and saving from single or compare modes
• extract utilities into their own file for clarity

Has this been tested? How?

manually

Screenshots (if appropriate)

Types of changes

(leave all that apply)

• New content or feature
• Refactor / chore

New frontend preview link is below in the Netlify comment 😎

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